Multiple relay networks, in which a source encoder communicates with a destination device through a number of relays, may be utilized for a wide range of applications. Activity in a multiple relay network may focus on Gaussian networks in which a first hop amounts to a Gaussian broadcast channel from a source device to relays, and a second hop to a multiple access channel between relays and receivers. Various transmission strategies, including decode-and-forward (DF), compress-and-forward (CF), amplify-and-forward (AF) and hybrid AF-DF, may be utilized for communication in such a network.
In a variation of a classical multi-relay channel, relays may be connected to the destination through digital backhaul links of finite-capacity. For example, this model may be utilized in cloud radio cellular networks, in which the base stations (BSs) may act as relays connected to the central decoder via finite-capacity backhaul links.
Pooling multiple relays into a distributed multiple-input multiple-output (MIMO) system includes a number of issues that may need to be addressed. High-performance operation of such systems may require a centralized data and channel processor, which may place significant throughput and latency requirements on the backhaul links which connect the relays to the centralized processor. For example, in cloud radio cellular networks, where base stations act as relays connected to the central decoder in the cloud, the backhaul problem may be acute because the links may have a finite capacity that may be insufficient for traditional approaches.